In scanning laser projectors, pixels are typically generated by modulating light from laser light sources as a scanning mirror scans the modulated light in a raster pattern. One continuing issue in scanning laser projectors is “speckle”. In general, speckle is an image artifact that can reduce the quality of projected images. Speckle occurs when a coherent light source is projected onto a randomly diffusing surface. When highly coherent light reflects off a rough surface, various components of the light combine to form patches of higher intensity light and lower intensity light. To the human eye or other detector with a finite aperture, these patches of variable intensity appear as speckles, as some small portions of the image look brighter than other small portions. Furthermore, these intensity differences can vary depending on observer's position, and thus the speckles can appear to change when the observer moves.
As such, speckle can significantly reduce the quality of image generated by a coherent source, such as laser in a scanning laser projector.